As an apparatus for spectralizing light comprising broad wavelength area and extracting monochromatic light, there is a monochromator which uses a diffraction grid or a prism as the dispersing element. The conventional monochromator using a diffraction grid was used for the purpose of providing a light source having a selected wavelength and selectively detecting the light to be detected from the target as a detector. For example, the monochromator for providing a light source is used in a spectrophotometer, for selecting the wavelength of the light source to be the target of analysis from the light source comprising various bands. Korean Patent Laid-Open No. 2008-0015759 discloses a monochromator system having a diffraction grid for separating light in order to have a specific wavelength range and resolving power.
FIG. 1 illustrates a general monochromator (100) using a diffraction grid. The monochromator (100) of FIG. 1 comprises a diffraction grid (110), a slit (120) to let light pass through restrictively, and mirrors (130, 140, 150) with flat or curved surfaces to adjust the route of the light. Specifically, once light with a broad wavelength band is provided to the monochromator, the mirror with a curved surface (130) changes the route of the light and the light is led to the diffraction grid (110). The diffraction grid (110) separates the wavelength of the incident light, and the slit (120) selectively passes through the desired wavelength bands in the separated wavelength bands by adjusting the position or the width, etc. of the slit. The light which passed the slit (120) passes again through the mirrors (140, 150) with flat or curved surfaces, and light having a specific wavelength is outputted from the monochromator.
However, the conventional monochromator using a diffraction grid has a problem that in the process of the incident light being scattered by the diffraction grid or being reflected or permeated by one or more of the mirrors, the efficiency of the light of a specific wavelength outputted from the device for the light incidentally irradiated to the device substantially decreases.
In order to solve this problem, Korean Patent No. 1,524,556 discloses a monochromator which can select the wavelength of the light by using a broadband filter. The patent realizes a monochromator without a diffraction grid by arranging in series one or more broadband filters that have different wavelength ranges of the light to be passed, thereby substantially increasing the efficiency outputted from a monochromator with respect to the incident light, compared to the conventional monochromator using a diffraction grid.
However, the monochromator has problems that a rotating device such as a separate electric motor is needed to change the rotating angles of the broadband filters, and as it comprises only one broadband filter group, it cannot output light of several wavelengths at the same time.